Cyclic Olefin Copolymer Microfluidic Devices for Forensic Applications

Abstract

Microfluidic devices offer important benefits for forensic applications, in particular for fast tests at a crime scene. A large portion of forensic applications require microfluidic chip material to show compatibility with biochemical reactions (such as amplification reactions), and to have high transparency in the visible region and high chemical resistance. Also, preferably, manufacturing should be simple. The characteristic properties of cyclic olefin copolymer (COC) fulfills these requirements and offers new opportunities for the development of new forensic tests. In this work, the versatility of COC as material for lab-on-a-chip (LOC) systems in forensic applications has been explored by realizing two proof-of-principle devices. Chemical resistance and optical transparency were investigated for the development of an on-chip presumptive color test to indicate the presence of an illicit substance through applying absorption spectroscopy. Furthermore, the compatibility of COC with a DNA amplification reaction was verified by performing an on-chip multiple displacement amplification (MDA) reaction.

Keywords: UV-VIS spectroscopy; cyclic olefin copolymer; forensic science; illicit drug analysis; microfluidic device; polymer bonding; polymer surface functionalization; presumptive forensic test.

Figure 1

Schematic representation of cyclic olefin copolymer (COC) chips for the color test with an optical path length of 2, 3, or 4 mm for integrated UV-VIS spectroscopy. The insets show chips with an optical path length of 4 mm. The top channel in the top right picture is filled with Allura Red.

Figure 2

Schematic side-view of the COC bonding process using the tacky layer method. It starts by adding a piece of filter paper to a Petri dish and soaking it with a mixture of acetone and cyclohexane. The chip parts were placed on top of the filter paper for 2 min, subsequently aligned, and a 2 kg weight was placed on top for 5 min.

Figure 3

Multiple displacement amplification (MDA) chips with (a) the schematic representation of the MDA chips with the used dimensions and (b) a chip filled with food dye to show the channel design.

Figure 4

Absorption measurement curves of the absorption of Allura Red in chips A, B, and C versus the concentration at a wavelength of 504 nm.

Figure 5

Absorbance measured at 500 nm for (a) acetylsalicylic acid dissolved in the Marquis reagent measured in COC chip D and (b) lidocaine dissolved in the Marquis reagent measured in COC chip A.

Figure 6

Absorption spectrum of benzodioxolyl-N-methylbutanamine (MBDB) dissolved in Marquis reagent with a concentration of 50 mM.

Figure 7

The amplification yield expressed in both concentration (ng/µL) and amount of dsDNA (ng) versus the amplification time with an input of 2.5 ng of purified DNA (TaqMan Control Genomic DNA). The error bars are ± 1 standard deviation.